1. Field of Invention
The present invention relates to a printing method, and more particularly to a printing method used when the resolution of a printing data is different from the distance between nozzles of a printing head.
2. Description of Related Art
When a printing method is used in industry to form an expected structure, the resolution of printing always changes with different application ranges, thus when a printing head of a fixed resolution is used for printing, the requirement on various printing resolutions cannot be satisfied. In order to solve this problem, various printing heads of different resolutions must be prepared for being replaced according to the different resolutions of the data to be printed. Thereby, the manufacturing cost and the process time for replacing the printing head are both increased. Moreover, whether a fitting printing head is available is another problem.
Moreover, the PCT Patent Application No. WO 02/098575 has disclosed a method of improving the printing quality of a microdeposition. The application is directed to controlling the ink drop size by the way of controlling the waveform of each nozzle or adjusting the drop number. Meanwhile, the resolution in the horizontal direction is increased by the way of generating an over-clocking signal with a control unit, and frequency division is performed by the way of adjusting the printing velocity of the printing head so as to achieve the goal of adjusting the resolution in the horizontal direction.
For example, FIG. 1A shows incorrect driving waveforms 370-1, 370-2, and 370-8 of the printing head, which cause the sizes or displacements of positions of a part of the corresponding ink drops 374-1, 374-2, . . . and 374-8 having errors. For example, the ink drop 374-4 is too small and incorrect in position, the ink drop 374-2 is too large and is also incorrect in position. By rotating the angle of a PMD printing head and adjusting the operation clock, as shown in FIG. 1B, correct driving waveforms 380-1, 380-2, . . . and 380-8 of the printing head and correct sizes and positions of the ink drops 384-1, 384-2, . . . and 384-8 are obtained.
Moreover, the PCT Patent Application No. WO 02/050260 has disclosed a microdeposition system, which is used to jet print a specific pattern on a substrate, and eliminates the defect of non-uniform density distribution due to the abnormal operation of nozzles. The patent application discloses that a mask is generated for jet printing a specific pattern, which is needed in the calculation of each jet printing process to calculate the data to be jet printed this time, so as to eliminate the defect of the non-uniform density distribution due to the abnormal operation of nozzles. FIG. 2A is a pattern to be formed, and a printing head 50 of FIG. 2B jets ink drops of predetermined positions in a plurality of rows 206-1 to 206-B according to nozzles 134-1 to 134-n. In the microdeposition system disclosed in this patent application, as shown in FIG. 2C, the pattern to be formed is obtained by a plurality of movements (as shown by marks 210 and 240) of the printing head 50 according to a mask generated by a mask generating device.
Moreover, in the PCT Patent Application No. WO 02/098573, a control unit is used to produce a jet printing waveform command, and send the command to the nozzle on the printing head, so as to produce the expected printed pattern, and the resolution of the printed image file is adjusted by the printing method of rotating the printing head. When a command of needing a nozzle to jet print is sent out by the control unit, a digital to analog converter (DAC) program device communicates with a memory and a controller, and produces a waveform voltage value to the nozzle. After receiving the voltage waveform, an OP amplifier corresponding to the nozzle performs the jet printing action.
FIG. 3 is a relative position of nozzles of a printing head and dots of a data to be printed according to a conventional printing method. As shown in FIG. 3, when the data with different resolutions needs to be printed, the printing resolution is changed by rotating the printing head. In FIG. 3, the printing head has nine nozzles, and after the printing head is rotated with an appropriate angle, each nozzle is aligned with a row of the dots. However, only three in nine nozzles are completely aligned with the dots. In other words, every time the printing head jets, only three nozzles functions instead of performing a full-hole jet printing. Thereby, the time for printing is increased. Moreover, it is needed to fill blank dots to the nozzles which are not aligned with the dots of the data to be printed. Thereby, additional time is spent on filling the blank dots, which causes the increase of the dots to be printed, and thus a memory of a larger capacity is required to store the data.